Psychrometric apparatus for direct reading of humidity



J. CRAPEZ Feb. 13, 1940.

PSYCHROMETRIC APPARATUS FOR DIRECT READING` 0F HUMIDITY Filed July 8, 1937 INVENToR JULES CRAPEz BY n ATToRN Ys metas sa. 1s, 1940 aisssss PATENT OFFICE lsimrrnosni'ruro mmrus Eon. maEc'r Hummm READING 0F Jules Grapes, Mons-en-Baroenl, France Application July 8, 1937, Serial No. 152,570

In France November 5, 1936 3 Claims.

The object of the present invention is a psychromatic apparatus, capable of indicating the hygrometric state of the air in a room or any premises without possible error due to reading graduated scales oi' two thermometers, a dry and a wet thermometer, by eil'ecting under determined conditions, a simple relative movement of one of the thermometers.

The object oi' the invention is to facilitate the rapid direct reading oi.' the hygrometric state of the air, arising or not from moistening of the air, of any industrial or private premises by aligning the levels of the thermo-metric columns of the two thermometers, the wet and dry thermometers, forming a psychrometer.

It is known that there exist dierentmethods for measuring the hygrometric state of the air, and a certain number of more or less perfected apparatus for determining the hygrometric state, of which among others the'apparatus termed a psychrometer, comprises two thermometers, one of which has its bulb surrounded by muslin which is constantly moistened.

Various tables give the hygrometric state oi.' the air` as avfunction of the temperature indicated on the wet thermometer and the diierences of the two temperatures indicated by lthe dry thermometer and the wet thermometer.

Devices have been investigated in order to give the value of the hygrometric state without having to determine these diilerences, but these render it necessary to read other numbers and then to memorize them in Aorder to correlate the readings of thermometersl on graduated scales or charts.

Qther devices avoid these errors due to readln or memorizing, but they necessitate a judicious selection among numerous v curves vor the use-of mechanical combinations which are sometimes vcomplicated and not free from errors.

It' is in order to overcome the diillculties and tedious operations necessitated by the apparatus hitherto used that it has been sought to obtain the psychrometer Adevice which will be described hereunder, and which device responds entirely to the purpose envisaged, its' special construction avoiding practically any error duev to reading or memorizing indications of ,t thermometric scales, while'l eliminatingin an absolute manner the errors arising due to the adjustment ot the apparatus in order to determine the hygrometric state investigated due to 'a particular conception of the application of relative mobility of one of the two thermometers.

It has been established that by arranging tables ot'readings oi! a psychrometer, in graphic form,

the values ot the wet thermometer plotted as ordinates and the differences between the values of the two thermometers, the wet and dry thermometers, as abscissae, all the values of the same hygrometric state are substantially in alignment and that this alignment is fairly exact fortemperatures from 10 to 35 degrees centrigrade, which is generally suillcient for the requirements of industry. f

For this reason the apparatus envisaged is based on a method ot displacing the dry thermometer in order to suitably bring the height of its thermometric column on a horizontal line passing through the height of the thermometric column of the wet thermometer. This movement is effected in such v a manner that the angle formed with the original position of ,this thermometer represents the hygrometric state indicated in tables by virtue oi the temperatures read on the dry thermometer and the wet thermometer.

This result isobtained' in practice by forming the dry thermometer rigid with a pointer, the upper end of which moves in a groove and the lower end ot which slides on a cam having a profile corresponding to the trace of this groove, that is to say this profile is such that for any displacement of the pointer, the point of intersection of the axis of the dry thermometer with the 'axis of the same dry thermometer in its initial position is alwaysy equidistant `from an yassumed zero curve.

Thus each angle formed for any displacement of the dry thermometer in order to bring the level of its thermometric column on the horizontal line through the level of the therrnometri'cv column of the wet thermometer, will correspond exactly to the hygrometric state indicated on a dial placed above the guide slot and the gradua- Qtions oi' which will correspond to the numbers given in the tables used with the ordinary psychrometer.

The invention `according to the invention is represented by wayof example in the accompanying drawing in which:

Figure 1 represents a view in elevation of the Figure i is a diagrammatic view oi the placement of the dry thermometer with respect to its initial position in order to determine the profile of the cam and the trace oi the guide slot.

Referring to the drawing it will be seen that the wet thermometer I is in a ilxed position while the dry thermometer 2 is mounted on a movable pointer 3. This pointer carries a lug or slide block 4 sliding yin a guide slot 5 the trace of which is sich that concurrently with the displacement of the lower end of the pointer, the point of intersection of the axis of the dry thermometer 2 with the axis oi its original position is equidistant from the zero curve; for example, in Figure 4, OA=O'A and OB =O"B. A bolt I passing through the block 4 locks the pointer 3 at the desired position. A bracket 'I attached to the back part of the pointer 3 carries a guide strip 8 sliding on a cam 9 of given proiile such that the intersection is obtained at the value desired for the alignment of hygrometric states of the sameyvalue.

The body of the apparatus is formed by a i frame with a faeeflo and behind this me is follows the ascending and descending motion of the arm I4 and thus remains horizontal.

The wire I1 is ilrst aligned with the end of the thermometric column of the wet thermometer I by operating on I2, and thenlthe pointer 3 carrying the dry thermometer 2 is moved by loosening the milled button I0 until the end of the thermometric column oi' this thermometer comes opposite the wire I1. The reading of the hirgro-- metric state is then effected on the dial 2l graduated as above mentioned and-placed above the guide slot 5 on the path of the end of the pointer.

In the .lower part of the apparatus is arranged ,a container 2I containing water which constantly supplies the covering or fabric 22 surrounding the bulb of the wet thermometer. The

thermometers I and 2 are arranged on the iront 4 of the apparatus', the thermometer I being on the pointer, in .order to be in front of the openings 23, which permits their natural or artificial ventilation.

It will be understood that iii being n0 longer necessary to read the temperatures indicated by.

Athe two thermometers I and 2 since'only the heights of the thermometric columns are considered, and since it is no longer necessary to interpret the interval between their readings there can no longer be any possibility of'errorv and thus the desired hygrometric state is obtained rigorously and exactly. 4

It will be noted that since the horinontal wire is in alinement with the levels ci the indicating columns of the two thermometers in order to effect a measurement of the hygrometric state. modincations of the hygrometric state arising subsequently can be rapidly determined.

Furthermore, it will be noted that to each point of intersection of the dry thermometer with the movable horizontal wire representative of the temperatures of the wet thermometer, there corresponds a known hygrometric state. It willthusbeeasytoindicateatthispointthe weight in grams of water vapour `contained in a cubic meter of air at the temperature and the hygrometric state considered.

These data may be arranged in the form of curves l, shown in Figure 1, and the reading may be effected by means of a wire 24 extending along the pointer 3 and movable therewith, the point of intersection of the wire 24 with the wire I'I representing a point lying upon one of the curves f. y

Figure d shows diagrammatically how the dry thermometer moves so that the pointer on which it is placed indicates on the divided scale the percentage of humidity ot the air.

The angles x, y, z, etc. i'ormed'by the intersecting axes 2 and 2', 2 and 2", 2 and 2"', are representative of the hygrometric states indicated in the tables and resulting from the alignment considered, for example:

l' Tempera- Tempere- Hygronture e( wat ture o( dry am' metric thumometer thermo state Degrees Degrees Percent 3l 2l l 0l l) 22 2 82 m 23 3 75 Itwillbeseenthatitiseasytodeterminethe proiile of the cam l as well as the path oi the g'uide slot guiding the upper hand of the pointer.

Supposethatitisnecessarytoknowthe hygrometric state corresponding to the temperatures indicated by the thermometric levels of the two thermometers, the wet thermometer I indicating 20, the dry thermometer 2 indicating 23. It is sumcient to operate the knob I2 so as to lower the horizontal wire I'I to a position indicated by the numeral I1' in order to bring it to the level of the thermometrlc column o! I indieating 20; When this operation has been eftected the milled knob I9 is loosened and the pointer is caused to take up position 3 such that the level of the thermometric column of thermometer 2 which moves to 2' may be opposite I1. The pointerl then being iixed in position by means of the knob Il the number I6 on thedial 2l can be read opposite the-hand o! the pointer which indicates that the hirglolnetric state investigated is '15%.

.Iordertoobtain atthe same time tl'ieweiglitV in grams o! water vapour contained in a cubic meter of air at the temperature co to this hygrometric state reference is' made to the curyesfandthatcurveisnotedwhichpasses throughthe point of intersection of the wire I1 in its position indicated by the numeral I1' and the wire 24 in the position indicated by the numeral24'i,vis.inthiscasethe lgramcurve. showingthattheremxiredresultis lgrams.

I claim: A

l. A psychrometric apparatus for the direct reading of hygrometrlc conditionst said apparatus comprising a frame, an immovable wet bulb thermometer carried by said frame, means movably mounted upon said frame and extending across the dry bulb thermometer for indicating the level o! mercury within said wet bulb .thermometer, a dry bulb thermometer movably mounted in said frame. and means connected with said frame to move manually said dry bulb thermometer in relation to said wet bulb thermometer to cause the levels of the two thermometers to coincide and nthat the anglebetween the original and iinai direc ons oi the longituf dinalaxilofiddrybulb Omeiielisrepamaca? resentative o! the hygrometric state as given by tables correlating the temperatures indicated by the two thermometers.

2. A psychrometric apparatus for thev direct reading of hygrometric conditions, said appara- .tus comprising a frame having a guide slot formed therein, an immovable wet bulb thermometer carried by said frame, a pointer, a slide block connected with one end of said pointer and movable in said guide slot, a dry bulb thermometer carried by said pointer, a member connected with the opposite end of said pointer, a cam connected with said frame and having a surface over which said member slides. the shape of said surface of the cam being such that the point of intersection of the axis of the dry bulb thermometer 1n its displaced position with the axis of the dry bulb thermometer in its initial position is equidistant from a zero curve and that the angle between the original direction and the nal direction of the longitudinal axis of the dry bulb thermometer resulting from bringing the level of mercury of the dry' bulb thermometer to the level of mercury of the wet bulb thermometer is representative of the hygrometric state as given by tables correlating the temperaturesl indicated by the two thermometers, means movably mounted upon said frame and extending across the dry bulb thermometer for indicating the level of mercury within said wet bulb thermometer, and a scale carried by said frame above said guide slotand having graduations corresponding to values given by tables usually employed in connection with psychrometers.

3. A psychrometric apparatus for the direct reading of hygrometric conditions, said apparatus comprising a frame having a guide slot formed therein, an immovable wet bulb thermometer carried by said frame, a pointer, means connected with one end of said pointer and movable in said guide slot, a dry bulb thermometer carried by said pointer, a member connected with the opposite end of said pointer,.

means connected with said frame and having a surface which is in frictional engagement with said member, the shape of said surface being such that the point of intersection of the axis of the dry bulb thermometer in its displaced position with the axis of the dry bulb thermometer in its initial position is Vequidistant from a zero curve and that the angle between the original direction and the nal direction of the longitudinal axis of the dry bulb thermometer resulting from bringing-the level of mercury of the dry bulb thermometer to the level of mercury of the wet bulb thermometer is representative of the hygrometric state as given by tables correlating the temperatures indicated by the two thermometers, a horizontal wire extending across both thermometers movable over said frame to indicate the level of the mercury column oi' said wet bulb thermometer, said frame being provided with a plurality of curves representing the Weight of water vapor in the air, a scale carried by said frame above said guide slot and having graduations corresponding to percentages of humidity in the air, and another wire carried bysaid pointer and extending parallel to the longitudinal axis o! said dry bulb thermometer, the point of intersection of the two wires in the displaced position of the pointer indicating a weight of water vapor as 

